Unless all I’ve read is BS, one of the reasons propeller-driven aircraft fell by the wayside was because the propellers themselves were by necessity becoming bigger and bigger. As they did so they became less and less efficient due to the tips traveling close to the speed of sound. The added drag and turbulence meant performance increases would require exponentially more power out of the engine.
My question is this. The GE9X has an 11' fan. How is it that this issue seemingly doesn’t apply to large turbofans? They are after all in basic operation glorified ducted propellers.